A conventionally known ventilation device ventilates a room while exchanging heat between outdoor air to be supplied into a room and room air to be exhausted to outside the room. For example, Patent Document 1 describes a ventilation device including a total heat exchanger allowing total heat exchange to occur between outdoor air flowing through an air supply passage and room air flowing through an air exhaust passage. If the concentration of volatile organic compounds (VOC) in a room is higher than a predetermined value, the ventilation device of Patent Document 1 determines whether the total heat exchanger has a region having a temperature lower than or equal to the dew point, based on temperature/humidity conditions inside and outside the room. In this case, if the total heat exchanger has a region having a temperature lower than or equal to the dew point, the ventilation device performs an operation for increasing the volume of ventilation air blown. This can facilitate discharging the volatile organic compounds to outside the room, and can reduce the concentration of the volatile organic compounds in the room to a level at which residents do not feel uncomfortable.